Regenerative fuel cell with ph control

The present invention relates to a process for operating a regenerative fuel cell (RFC). The process involves circulating a first electrolyte (electrolyte 1) through the negative chamber of the cell and a second electrolyte (electrolyte 2) through the positive chamber of the cell. Electrolyte (1) contains sulfide during the discharge cycle of the cell. Electrolyte (2) contains bromine during the discharge cycle of the cell. Decreases in ph in the electrolyte are compensated by circulating a fraction of other electrolyte (1) or (2) through the positive chamber of an auxiliary cell. A fraction of electrolyte (2), which has been made free of bromine, is circulated in the negative chamber of the auxiliary cell.